Conventionally, wiring is formed in micro wiring grooves, holes, and resist openings provided in a surface of a semiconductor wafer or the like, and a bump (a protruding electrode) that electrically connects to an electrode of a package or the like is formed on the surface of the semiconductor wafer or the like. Examples of known methods for forming the wiring and bumps include an electrolytic plating method, a deposition method, a printing method, and a ball bump method, but the electrolytic plating method, with which performance is relatively stable and miniaturization is possible, is increasingly being used with an increase in the number of I/Os, and a reduction of the pitch between the I/Os, of semiconductor chips.
When forming a bump by the electrolytic plating method in a predetermined position on a substrate on which wiring is formed, a resist is generally used as a mask. That is, a seed layer is formed as a power supply layer on a surface of the substrate, and a resist having a height of 20 to 120 μm, for example, is applied to the entire surface of this seed layer. Then, an opening having a diameter of approximately 5 to 200 μm, for example, is provided in a predetermined position in this resist layer, and a resist pattern is formed. Then, an ashing process is performed to remove resist residue on the substrate by irradiating ultra violet (UV) light onto the substrate on which the resist pattern has been formed (see Japanese Patent Laid-Open No. 5-315339, for example). When the ashing process is performed, organic matter adhered to the seed layer of the substrate is removed, and the resist surface also becomes hydrophilic. Hydrophilic treatment (descum process) is also sometimes performed to improve the wettability of the surface to be plated by irradiating O2 plasma onto the resist surface of the substrate (see Japanese Patent Laid-Open No. 2012-114256, for example). A plating apparatus that includes an ashing device that ashes the resist surface of the substrate is also known (see Japanese Patent Laid-Open No. 2005-240108).